Electron discharge device



H. STEELE, JR ELECTRON nIsHARcE DEVICE Aug 15, 1950 Filed Feb. 12, 19,48

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BY MLu muL ATTORNEY Patented Aug. 15, 1950 UNITED STATES PATENT OFFICE ELECTRON DISCHARGE DEVICE Howard L. Steele, Jr., Bloomfield, N. J., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application February 12, 1948, Serial No. 7,767

Claims. (01. 250-275) This invention relates to electron discharge devices which utilize acavity resonator, or cavity resonators, and a velocity modulated beam of electrons therethrough, and for brevity will be avoid obstructions. in the-beam path and at the same time provide a construction wherein 'the emissive surface of. the secondary electron emitting electrode is not in the the primary cathode.

path of.sight=..of.

Once again, an object of the invention is to suppress oscillation of electrons across the resonator gap and to suppress hysteresis.

Other objects of the invention will appear to referred to herein, as often occurs in the trade, 5 those skilled in the art to which it appertains as a resonator beam converter. as the description proceeds both by direct recitae During the past several years development of tion thereof and by implication from the context. these converters has resulted in production of Referring to the accompanying drawing in three distinct types; namely, first, those wherein which like numerals of reference indicate similar two or more resonators are employecl'and the 1 parts throughout the several views: beam makes a one way transit from a cathode to Figure 1 is a longitudinal sectional view of a a collector; second, those known as reflex concavity resonator converter constructed in acverters wherein the beam travels from the cordance with my invention; cathode towarda reflector and then is reversed Figure 2 is a cross-sectional view looking toin direction traveling over apart at least of ward the secondary emitter, taken on line the primary path; and third, those known as IIII of Figure 1; and secondary emissive converters wherein a sec- Figure 3 is a sectional view looking away from ondary emitting cathode replaces the reflector of the secondary emitter as uponline III- II of the second type for returning secondary elec- Figure 1. 1 trons to the single resonator. The present inven- '20 In the specific embodiment of the invention tion relates more particularly to the last menillustrated 'in' said drawing, there is shown a tioned type. 1 resonator beam converter fabricated as a body It is generally recognized in the trade that the of revolution about an axis and providing a secondary emissive converter is more efiicient coaxial hollow resonant chamber, herein desiginitially, but that the proportionately greater nated resonator l0. efficiency over the other types is maintained for The converter provides an evacuated enclosure only a portion of the effective tube life and that within which is a primary cathode ll transverse the change of efliciency is detrimental to use to and symmetrical upon said axis opposite one in the field, end of the resonator, and an opposed electrode Accordingly, an object of the present inven- I2 which functions as an anode with respect tion is to provide a secondary emissive'converter to cathode l I and which is also transverse to and wherein a high efficiency will be maintained for symmetrical upon the axis and at the opposite a longer period than heretofore, and specifically end of the resonator from said cathode. Said for the life span of the converter. electrode l2 provides a middle portion l3 hay-- Another object of the invention is to maintain 5 ing a hollow l4 directed toward the cathode, and a copious yield of secondary emission throughprovides an annular substantially fiat ring porout the lifespan of the converter. l tion [5 radiating from the open end of said Closely related to the foregoing object, the hollow. The surface [6 of said ring portion of present invention has an objective-of preventing said electrode which is directed toward thecontamination of the secondary emissive elec- 40 cathode is emissive of secondary electrons and is trode. 4 i i here shown as having secondary emissive mate- Again, an object of the invention is to provide rial thereon constituting the said surface It of a structure embodying minimum modificationoi the electrode. There are various materials existing constructions of .cavity resonator 0011- known to be emissive of secondary electrons, of verters. I r 5 which silver magnesium is an example. corollary to the foregoing bject is a further It is the secondary emission from saidsurdesideratum of maintaining conventional dimenface [6 of ring-portion l5 of said electrode I2 sions of present day converters in manufacture which goes back toward the cathode, gives up of the present invention. 6 i energy thereto .at a desired frequency of oscilla- Yet again, an, object of the invention isto' tion in the resonator and produces the output energy by loss of energy of the secondary electrons to the resonator. In order'to obtain return of secondary electrons to the resonator, proper polarities are applied by batteries or other sources of potential (not shown) to thecathode,

secondary emitter, and resonator. It is necessary to have the secondary emitter more positive than the cathode, and usually, although not always necessary, to have the resonator more positive than the secondary emitter.

The converter furthermore provides a beam passageway partway through and coaxial to the resonator and comprised by .the hollow interior of a cylinder H situated between the cathode and resonator and with a portion of the cylinder projecting into the resonator so that a constriction or gap I8 is provided between the end of said cylinder and the end of the resonator furthest from the cathode. According to the present invention, the end of the cylinder i? nearest the cathode is partial y closed by a disc 19, said disc having a central opening 28 therein. Similarly, the opposite end of the cylinder H is closed by a disc 2| having a central opening 22 therein. The end wall of the resonator through which cylinder I! protrudes comprises a flexible diaphragm 23 sealed to said cylinder and sealed to the peripheral wall 24 of the resonator, which enables said cylinder to be adjusted with respect to the forward or fixed end 25 of the resonator, for tuning purposes. Between the cathode and said cylinder I1 is a focusing or electron restricting collar 26 which is shown frusto-conical in shape with the smaller end thereof toward the cathode. Contiguous to but electrically separate from the smaller end of the focusing collar i a focusing grid 21 thereacross and parallel to the cathode and also in close proximity thereto. The diameter of the smaller end opening of the focusing collar determines the maximum possible diameter of beam which can proceed therethrough toward the secondary emissive electrode. The focusing collar 25 and rid 2'! are separately supported by suitable means such as the respective cylindrical metallic supports 26a and 21a which in turn are carried by the cathode insulator Ila.

The size of this opening as well as the size of the openings 20 and 22 in the discs at the ends of the cylinder I1, and the size of the hollow 14 in the secondary emitting electrode have definite relationship to each other, such that a straight line from any part of the area of the opening through the focusing shield directed forwardly through the openings of the cylinder I? will intercept the secondary emitter electrode only within the hollow 14 thereof and not upon the portion 85 which has the secondary emitting face I6. Consequently, any electronic or other discharge from the cathode moving in straight lines therefrom to the secondary emitting electrode, cannot enga e the secondary emitting surface. This restricted path from the cathode to said electrode will be referred to herein as lines of-sight.

Contamination of a secondary emitting surface from a primary cathode may result from particles from the cathode, and since such particles have a considerable mass in comparison to electrons those particles are '-n0t subject to deflection by electrostatic forces existing in a converter of the character described, and therefore will travel in a straight line and thus will be restricted to the line-of-sight path in travel to the hollow 1.4 in the present showing and will notstrike the secondary emitting surface it. Similarly, uncharged particles of matter such as vaporized material evolved from the cathode during operation thereof travel in straight lines and. are not influenced by electrostatic conditions along the path of travel, and therefore this source of contamination to which secondary emitting cathodes are susceptible, will not exist in the construction of the present invention since the secondary emitting material is removed from any straight line travel of matter of line-of-sight from the cathode.

On the other hand, electrons, being charged negative particles, may be deflected from the straight path, and that characteristic is made use of in the present invention. Between the fixed Wall 25 of resonator IE and the secondary emissive electrode I2, I provide an electron influencing member 28 here shown as a cylindrical collar secured to the said resonator wall 25 projecting toward the secondary emitting electrode I2 with its forward edge in proximity to said electrode near the perimeter thereof. The said member 2'8, by virtue of its support upon and attachment to the resonator iii, will have the same potential polarity as the resonator and. is in any event more positive than the cathode. The electrostatic influence of this polarity upon the primary electrons from the cathode deflects the same away from the axis of the beam, or line-of-sight path thereof, as indicated by dotted line 29, and thus causes the electrons to impinge upon the secondarycmitting surface l6. Since the secondary emissive surface will emit electrons in consequence of the impinging of the primary electrons upon the said surface, the secondary electrons are likewise influenced by the potential of said member 28 as they move toward the resonator and therefore tend to spread away from theaxis or line-of-sight, as indicated by dotted lines 30. An enlarged opening Si is provided in end wall 25 of the resonator adequate to pass the diverted or spread-out stream of secondary electrons. The secondary electrons pass through the large central opening 3| in the fixed end wall 25 of the resonator and phase relation is adjusted so they give u genergy to the resonator in traversing the gap between said fixed wall and disc 2|. This combination of the spreading of the primary beam electrons and of the secondary stream of electrons causes the secondary electrons to'avoid the line-of-sight path and to be diverted to engage the solid portion of disc 2| in the resonator, which accordingly acts as a collector. Due to the spreading or umbrella action of the secondary electron beam above described, the secondary electrons will not be in a path through hole 22 of said disc 2! but all will engage the disc and be stopped thereby. The frequency at which the resonator operates depends upon what part of the radio frequency cycle the bunch of secondary electrons, represented by dotted lines 36, arrive in the gap I 8. Without umbrella effect some of these electrons could pass completely through the gap and be available for another transit of the gap. These multiple transit electrons also influence the frequency .of the cavity in similar manner. The number of multiple transits depends not only on the voltage of the secondary emitting element I2 but also upon the direction the voltage was made to approach the given voltage. The present invention eliminates the multiple transits and the accompanying hysteresis. Consequently, there is no oscillation of the secondary electrons back and forth with respect to the gap 18 between disc 2! and fixed wall 25 and thus no opportunity is presented for the electrons to introduce hysteresis or get out of phase and absorb any energy from the resonator.

If' so desired, the; hollow portion l3 of the secondary emissive electrode may have water or other fluid cooling associated therewith. As shown, the said portion [3 is secured in the mouth end of a cup-shaped coupling 32 which in turn is sealed to the end margin of a tube 33 which extends axially outward from the device and has appropriate vacuum sealing attachment to the fixed wall of the resonator by intervening structural parts, such as thimble 34, glass sleeve 35, metal joining sleeve 38, metal dome 31 and resonator head plate 38. The said tube 33 has a smaller tube 39 therein, the two tubes being utilized for fluid circulation which may be accomplished by using the smaller tube for entry of the fluid and the larger tube for discharge of the same to and from a chamber 40 within coupling 32 and next the end of portion 13 of the secondary emissive electrode. It will be understood that the Converter is appropriately evacuated and sealed so that the electrons are discharged and remain in vacuum in their travel. Furthermore energy developed in the resonator may be conveyed therefrom in suitable manner as by an output loop 4! and its associated coaxial sealed output line 42.

The further structural detail may be mentioned that mechanical tuning is effected by vary- 7 ing gap l8 and to do this cylinder I is flanged at 43 at its end which protrudes from the resonator and the flange is sealed to a head plate 44 to which the cathode enclosure 15 is also sealed. Springs 46 tend to draw headplates 38 and 44 toward each other and adjustable screw props 41 between the plates hold them apart to desired extent.

It also may be added, that discs [9 and 2| in the ends of the beam passageway cylinder l1 act as grids for the primary beam electrons. A positive potential from a suitable source is applied to the resonator and discs l9, 2| and member 28, said potential being more positive than that which is applied to the cathode and preferably more positive than that which is applied .to the electrode I2 in order that the direct current field of member 28 maybe properly effective in controlling and deflecting the electron stream away from the axis or line-of-sight and also in order that the primary electrons passing forwardly through the accelerating field in the resonator may instigate secondary electrons from the secondary emissive face of electrode 12 that they may reach position in gap E8 of the resonator in phase. with the field at a time when the field is decelerating .to the secondary electrons. tential gradient and distance ofthe secondary emitting surface Hi from the resonator gap [8 determines the positions attained by a primary electron and the secondary electrons instigated thereby during a phase change period of. oscillation." The" ideal desideratum is that a primary electron passing through and at a given reference position in the gap 18 0f the resonator at phase condition ofthe oscillating field which is most accelerating to the electron, -shallcomplete its transit to the'secondaryemitting surface It and instigate secondary electrons therefrom, which, starting at zero velocity, shall reach the said reference position of the primary electron in the resonator gap I8 when the oscillating field has reversed, which means 180 change, so the field will then be most decelerating to the secondary electrons. It is well known, but may be mentioned, that passage of the primary electrons through the radio frequency field in gap [8 of the resonator induces bunching'of the electrons which is complete by the time the electrons im-r pinge upon the secondary emitting surface.- The amount of secondary emission" yield i proportional to the amount of primary electrons effective on the secondary emitting surface. Since'the primary electrons are bunched, the charge density varying 'asit arrives at the secondary emissive surface, the secondary electrons will be exactly bunched in correspondence therewith.--

The yield of the secondary emission .will' be: greater than unity. Lateral deflection of the primary electron causes them to impinge upon. the secondary-emissive surface and that surface,- being out of line-of-sight of the cathode is keptfree of contamination from the cathode. Furthermore, deflection of the secondary electronsfrom the path of the primary electrons and catching of the secondary electrons on first passage into the resonator prevents hysteresis in the curve of secondary emitter voltage against frequency of the output.

I claim:

1. An electron discharge device comprisinga resonator, means adjacent said resonator for producing and passing primary electrons through said resonator, an opposed electrode at the opposite side of the resonator from said electron producing means, said electrode having a nonemissive area in line-of-sight from said electron producing means and having a, secondary emitting surface outside of said line-of-sight, and

electron deflectin means between said resonator and surface for deflecting primary electrons from the non-emissive area to the emissive surface of said electrode in approach of said electronstoward the said electrode.

2. An electron discharge device comprising a resonator, means adjacent said resonator for producing and passing primary electrons through said resonator, an opposed electrode at the op posite side of the resonator from said electron producing means; said electrode having anonemissive area in line-of-sight from said electron producing means and having a secondary emitting surface outside of said line-of-sight, and an annular electron deflecting member between said resonator and surface for deflecting primary electrons from the non-emissive area to the emissive surface of said electrode in approach of said electrons toward the said electrode, and for deflecting secondary electrons away from thepath of the primary electrons. 3. An electron discharge device comprising a resonator having a beam' passageway cylinder projecting thereinto and protruding therefrom at one end thereof, a cathode opposite the protrud ing end of said cylinder, a secondary emissive electrode at the opposite end of saidresonator from said cathode, means in said cylinder for restricting line-ofesight between said cathode and electrode, said electrode having its secondary emissive surface entirely outside of said line-of; sight, and electron deflecting means between said resonator and surface-for deflecting electrons in transit to or from and between said surface and resonator.

4. An electron discharge device comprising a resonator having a beam passageway cylinder projecting thereinto and protruding therefrom at one end thereof, a cathode opposite the protruding end of said cylinder, an opposed electrode at the opposite end of said resonator from said cathode, means in said cylinder for restricting line-of-sight between said cathode and electro'd'e, said electrode having a non-emissive area in line-of-sight from said cathode and having a secondary electron emitting surface outside of said line-of-sight, and electron deflecting means between said resonator and electrode for defleeting electrons in transit to and from and between said surface and resonator.

'5. An electron discharge device comprising a resonator having a beam passageway cylinder projecting there-into at one end thereof, said cylinder having a centrally apertured disc in the end thereof within the resonator, a cathode opposite the other end of said cylinder, a secondary emissive electrode at the opposite end of said resonator and cylinder from said cathode, said disc confining the line-of-sight between said cathode and electrode, and means proximate to said line-of-sight for deflecting secondary electrons away from said line-of-sight whereby said disc radially outside of its aperture intercepts secondary electrons from said electrode.

6. An electron discharge device comprising a resonator, a cathode at one end of said resonator, an electrode at the opposite end of said resonator, said electrode having hollow central portion directed toward the resonator and on a common axis therewith and with said cathode, and said electrode having a surface transverse to said axis extending outward from said hollow portion and having its face toward the resonator emissive of secondary electrons, and electron influencing means offset laterally from said axis for diverting primary electrons from the cathode into engagement with said face.

'7. An electron discharge device comprising a resonator, a cathode at one end of said resonator, an electrode at the opposite end of said resonator, said electrode having a non-emissive hollow central portion directed toward the resonator and on a common axis therewith and with said cathode and said hollow central portion intercepting the entire line-of-sight of the electrode from the cathode, and said electrode having a surface transverse to said axis extending outward from said hollow portion and having its face toward the resonator emissive of secondary electrons, and electron influencing means onset laterally from said axis for diverting primary electrons from the cathode into. engagement with said face. I

8. An electron discharge device comprising a resonator, a cathode at one end of said resonator, an electrode at the opposite end of said resonator, said electrode having a non-emissive hollow central portion directed toward the resonator and coaxial therewith and with the cathode, means between the cathode and electrode confining the line-of-sight between the cathode and electrode to the diametrical area of said hollow central portion of the electrode, said resonator having an opening in its wall toward the electrode of greater diameter than said hollow central portion of the electrode, said electrode having a, surface emissive of secondary electrons, and electron influencing means offset from the line-of-sightbetween said electrode and cathode tor diverting secondary electrons emitted from 8 said surface away from said line-of-sight' for entry through said opening of greater diameter into said resonator.

9. An el ctron discharge device comprising a resonator, a cathode at one end of said resonator, an electrode at the opposite end of said resonator, said electrode having a non-emissive hollow central portion directed toward the resonator and coaxial therewith and with the cathode, and said electrode having a surface transverse to said axis extending outward from said hollow portion and having its face toward the resonator emissive of secondary electrons, means between 1e cathode and electrode confining the lineoi sight between the cathode and electrode to the die-metrical area of said hollow central portion of the electrode, said resonator having an opening' in its wall toward said electrode of greater diameter than said hollow central portion of the electrode, and electron influencing means ofiset from the line-of-sight between said electrode and cathode for diverting primary electrons from said cathode away from the line-of-sight and into engagement with the said secondary emissive surface of said electrode and for diverting secondary emitted electrons away from said lineof-sight and through said opening of the resometer.

10. An electron discharge device comprising a resonator, a cathode at one end of said resonator, an electrode at the opposite end of said resonator, said electrode having a non-emissive hollow central portion directed toward the resonator and coaxial therewith and with-the cathode, and said electrode having a surface transverse to said axis extending outward from said hollow portion and having its face toward the resonator emissive of secondary electrons, a, beam passageway cylinder between the cathode and said electrode and with an end thereof within the resonator and'directed toward said electrode, a disc at said end of the cylinder, said disc having an opening therein confining line-of-sight from the cathode to a restricted area of the said electrode, and said electrode being emissive of secondary electrons at a part thereof outside of said restricted area, said resonator having an opening between said disc and electrode of greater size than said restricted area of the electrode, and electron deflecting means between said disc and electrode for deflecting primary electrom to the secondary emissive part of the said electrode and to deflect secondary electrons away from the opening of said disc, said secondary electrons being directed through the opening in said resonator and said disc functioning as a collector for the secondary electrons.

HOWARD L. STEELE, JR.

. Name Date Parker Feb. 25, 1947 Number 

